In a manufacturing facility, items such as work-in-process parts or processing tools and apparatus are frequently transported between parts storage facility, processing stations and various other places in a fabrication plant. Some of the items transported are wet or contain a liquid because they have been processed in a wet bench process or otherwise in a process where liquid chemicals are used, i.e., frequently the case in a semiconductor fabrication facility. For instance, wafers that are stored in a pod after being processed in a chemical mechanical polishing apparatus are still wet because of the liquid polishing compound left on the surface of the wafers. As a result, wet cassettes or other wet processing accessories and tools are transported between processing stations on a push cart or trolley.
In order to avoid liquid from spilling to lower trays in the push cart, a container is often designed in the trays. After usage, the container in the push cart is frequently in a wet condition. This causes numerous processing difficulties and problems. For instance, the liquid may damage other parts that are also stored in the same container. The liquid may splash out of the container and thus wet the factory floor either causing a safety hazard, or when the liquid is an acid or an alkaline, the floor may be damaged in addition to the possibility of personal injuries. Moreover, the container must be emptied periodically by operator to dispose the liquid contained therein. The manual dumping of liquid from the container is laborious and may cause personal injury upon contact with the liquid.
In a semiconductor fabrication facility where chemical mechanical polishing apparatus is widely utilized, it has been noticed that push carts used to transport wet cassettes (which contains wet wafers) must have their containers in the trays emptied every 4.about.6 hours. This becomes a tedious and time consuming process, in addition to the processing problems discussed above.
It is therefore an object of the present invention to provide a vehicle for transporting wet objects in a factory that does not have the drawbacks or shortcomings of the conventional push carts.
It is another object of the present invention to provide a vehicle for transporting wet objects in a semiconductor fabrication facility that does not present the danger of personal injuries when liquid chemicals are involved.
It is a further object of the present invention to provide a vehicle for transporting wet objects in a semiconductor fabrication facility where wet cassettes after a chemical mechanical polishing process are being transported.
It is another further object of the present invention to provide a push cart for transporting wet objects in a semiconductor fabrication facility wherein horizontal liquid-collecting trays equipped with an inclined bottom panel and a perforated top panel are utilized.
It is still another object of the present invention to provide a push cart for transporting wet objects in a semiconductor processing facility wherein horizontal liquid-collecting trays are installed in the push cart and each of the trays is provided with a drain hole for draining liquid into a liquid drain tank mounted at the bottom of the push cart.
It is yet another object of the present invention to provide a push cart for transporting wet objects in a semiconductor processing facility wherein liquid is collected in a drain tank positioned at the bottom of the push cart and fabricated in a substantially transparent material such that liquid level in the drain tank can be readily observed.
It is still another further object of the present invention to provide a push cart for transporting wet objects in a semiconductor fabrication facility wherein horizontal liquid-collecting trays are utilized and each tray is equipped with a drain hole for draining liquid into a drain tank through a liquid drain pipe in fluid communication with the drain holes.
It is yet another further object of the present invention to provide a push cart for transporting wet objects in a semiconductor fabrication facility wherein three horizontal liquid-collecting trays are provided in the push cart each equipped with a drain hole for draining liquid into a drain tank positioned at the bottom of the push cart.